Engineering publish/subscribe systems and event-driven applications

Driven by advances in information and communication technology, computing infrastructures continue to grow in size and complexity while people increasingly depend on them. To better master their inherent scale and complexity, modern computing systems are often designed to be self-managing. They are aware of their state as well as of their environment so that they can dynamically react on changes caused by internal or external events in order, for example, to adapt and optimize their configuration or to better support and assist their users. Publish/subscribe systems provide a versatile basis for building distributed eventbased infrastructures. Components communicate by publishing notifications about occurred events and by subscribing to those notifications of interest. The resulting characteristic loose coupling between participating components is both a big strength and a severe weakness. On the one side, the indirect communication decouples components in space, time, and control flow and, thereby, provides the flexibility and extensibility required by modern event-driven applications. On the other side, when systems grow in size, it becomes difficult or, in practice, even impossible to keep track of all effects and side-effects that may be caused by a published notification. In this thesis, we address the latter problem and develop structuring means to modularly design and engineer large-scale event-based infrastructures. We consider modularity and related engineering aspects at the level of the architecture, the middleware, and the application. For publish/subscribe systems, we propose a broker architecture based on the concept of features and their composition. This way, middleware developers can easily modify, extend, or add individual broker features in order to tailor the overall functionality to actual application requirements and environment conditions. We show how features are implemented as pluggable broker components and discuss interfaces and guidelines for their composition. With scoping, we present a module concept to structure publish/subscribe networks and event-driven applications. Scopes bundle related components to new application artifacts providing them an isolated environment for interaction. Therefore, the visibility of a notification is restricted to components of the same scope only, unless the scope interface allows its exchange with other components. Scopes can flexibly be arranged in hierarchies that help decomposing applications